Hey guys, I'm in a college trig class and these questions were on my last test. I thought I had trig identities down but I barely know where to start on these ones. Can you help me out?

1. 12sin(2t)cos(3t)+20sin(2t)-cos(3t)-5=0

2. 6sec(2t)^2-13sec(2t)=6

3. 2sin(x)cos(-x)=2sin(-x)sin(x)